Use of devices adapted to ultrasonically weld electric conductors, preferably in stranded form, has become a preferable method of welding in electronic industry. An ultrasonic welder is typically provided with a welding tip which produces ultrasonic vibration and an anvil as a mating tool. The anvil includes a plurality of faces, each movable along a linear path to define a space in which the conductors can be compressed to varying dimensions while ultrasonic vibration is being applied to them. When the anvil is closed and the conductors are being compressed to one another, the anvil faces form a peripherally closed compartment. When the anvil is open, the end faces are left open for the conductors to pass through it.
A device of this type is known from U.S. Pat. No. 4,867,370 to Welter et al. (Welter '370), where provision is made for variously dimensioned wires which are to be welded while maintaining a tight grip around the conductors.
FIGS. 1-4 of this application illustrate a mode of operation of Welter '370 that starts with having a wide open working area 4 receiving a bundle of wires 2 loosely inserted in this area. Upon positioning the wires in an arbitrary manner, components forming the working area move inwardly to tightly enclose the wires to be welded. As is disclosed in Welter '370, displacement of the components is a function of the fineness of wire ends and is sequenced to move a gathering block 6 following moving of anvil 16 and welding tip 8 to reduce the working area, as illustrated in FIGS. 1-3. Finally, as shown in FIG. 4, subsequent to the welding of the wires, the gathering tool moves away from the working area beyond its initial position, and then it is displaced back to its initial position.
It has been found that there is a greater efficiency of welding wires that are vertically stacked between a vibrating horn and stationary anvil, as compared to those wires that are adjacent to each other. The above discussed reference is representative of the state of art and discloses a multiplicity of wires many of which are positioned adjacent to each other along a welding surface of the tip. Others, however, although welded in a vertical plane tend to fill interstices between subsequent wires of the adjacent column and welded diagonally therewith which produces a relatively inefficient weld. As a consequence, some welds are weaker than others based on the way the wires have been loaded.
It is, therefore, desirable to provide an ultrasonic welding apparatus for wire splicing which automatically sets the position of the tooling so as to restrict a wire nest and require the operator to stack the wires in at least one vertical row extending from a welding tip. It is also desirable to provide a method of operating the ultrasonic apparatus and allowing the tooling to move away from the wire nest for a predetermined period of time, and subsequently to move back in an initial position characterized by a preset width.